The present invention is directed to foams having improved flame resistance. In particular, the foams of the invention are closed celled rigid polyurethane or urethane-modified polyisocyanurate.
A critical factor in the large scale commercial acceptance of rigid polyurethane foams in the building insulation industry has been their ability to provide a good balance of properties. Rigid polyurethane foams are known to provide outstanding thermal insulation, excellent fire performance and superior structural properties, all at reasonably low density. Such rigid foams are (in general) prepared by reacting the appropriate polyisocyanate and isocyanate-reactive compound in the presence of a blowing agent. Chlorofluorocarbon blowing agents (CFCs) such as CFC-11 (CCl3F) and CFC-12 (CCl2F2) have been the most commercially important blowing agents primarily because of their good thermal insulating properties and low or non-flammability. Use of such blowing agents has been a key reason for the good balance of properties of rigid polyurethane foams. Recently, CFCs have been associated with the declining ozone concentration in the earth""s atmosphere and their use has been severely restricted. Hydrochlorofluorocarbons, especially HCFC-141b (CCl2FCH3) and HCFC-22 (CHClF2) have become the interim solution in many applications, once again due to their good thermal insulating properties and low or non-flammability. HCFCs still have an ozone depletion potential and their use is under constant scrutiny. The production and use of HCFC-141b is presently scheduled to end by the year 2003 in the USA.
Such environmental concerns have led to a need to develop reaction systems which utilize blowing agent(s) having a zero ozone depletion potential while retaining the good balance of properties for which rigid polyurethane foams are known. A class of materials which have been investigated as such blowing agents are hydrofluorocarbons (HFCs), for example: 1,1,1,3,3-pentafluoropropane (HFC-245fa); 1,1,1,3,3-pentafluorobutane (HFC-365mfc); 1,1,1,2-tetrafluoroethane (HFC-134a); 1,1-difluoroethane (HFC-152a). There are numerous patents and literature references on the use of HFC""s as blowing agents for rigid polyurethane foam. The use of such materials is disclosed, e.g., in U.S. Pat. No. 5,496,866 (Bayer); U.S. Pat. No. 5,461,084 (Bayer); U.S. Pat. No. 4,997,706 (Dow); U.S. Pat. No. 5,430,071 (BASF); U.S. Pat. No. 5,444,101 (ICI). Although HFCs are environmentally more acceptable than CFCs and HCFCs, they are inferior in fire properties. The polyurethane foams prepared using the HFC blowing agent must have good fire properties while retaining the good thermal and structural properties, all at densities comparable to those possible with CFC and HCFC blowing agents. Fire properties are especially important for rigid polyurethane foams used in the building industry as they must meet strict fire resistance codes.
At present, hydrofluorocarbons and hydrocarbons are the two leading classes of materials that are being evaluated by the rigid foam industry as zero ozone depletion potential (ODP) blowing agents. Neither of these two materials has all the attributes of an xe2x80x9cidealxe2x80x9d blowing agent. For example, the global warming potentials of HFCs are high (lower than CFCs but still high by some accounts) but the VOC content is low. Hydrocarbons have extremely low direct global warming potential but they are considered VOCs.
Thus, there still remains an unfulfilled need to develop reaction systems in which blowing agents have a zero ozone depletion potential, and which produce foams with good balance of properties for which rigid polyurethane foams are known.
Therefore, it is the object of the present invention to provide closed celled rigid polyurethane or urethane-modified polyisocyanurate foams which have, even when blown with hydrofluorocarbons, equivalent or improved fire resistance properties than CFC or HCFC blown foams.
It is another object of the present invention to provide closed celled rigid polyurethane or urethane-modified polyisocyanurate foams blown with hydrofluorocarbons which have good thermal insulation and structural properties along with the improved fire properties.
It has now been unexpectedly discovered that the use of over 40 weight % of aromatic polyester polyols of average functionality lower than 3.0 as the polyfunctional isocyanate-reactive composition, along with the use of organo-phosphorous compounds in the foam formulation improves the fire properties of polyurethane foam prepared in the presence of HFC blowing agents. Such HFC blown foams also have surprisingly good thermal insulation and structural properties along with the improved fire properties. The compositions of the present invention advantageously make it possible to obtain the balance of properties best suited to meet both the commercial and environmental demands of the present times.
It has now surprisingly been found that rigid polyurethane foam having a density between 1.2 to 4.2 lb/cu.ft. with excellent fire properties and good thermal and structural properties can be obtained by using the formulation
(1) organic polyisocyanates,
(2) a blowing agent comprising
(a) C1-C4 hydrofluorocarbons which are vaporizable under the foaming conditions as the physical blowing agent, and
(b) water
(3) polyfunctional isocyanate-reactive compositions containing over 40 weight % of aromatic polyester polyols of average functionality lower than 3.0,
(4) organo-phosphorous compounds, and
(5) one or more other auxiliaries or additives conventional to formulations for the production of rigid polyurethane and urethane-modified polyisocyanurate foams. Such optional additives include, but are not limited to: crosslinking agents, foam-stablilising agents or surfactants, catalyst, infra-red opacifiers, cell-size reducing compounds, viscosity reducers, compatibility agents, mold release agent, fillers, pigments, and antioxidants, wherein the amount of said organo-phosphorous compound used is such that the amount of phosphorous is between about 0.01 to about 2.5% by weight, based on the total weight of the foam forming reaction mixture.
In summary, the surprising technical advantages of this invention are the discovery of rigid polyurethane foam formulations blown using hydrofluorocarbons (zero ODP) blowing agents which give foams whose fire performance in laboratory tests are equal or superior to those foams blown with CFCs or HCFCs; structural performance, such as compressive strength and long term dimensional stability, is comparable or better than foam blown with CFCs or HCFCs; and initial and long term insulation performance comparable to those foams blown with CFCs or HCFCs.
The foams of the present invention are suitable for use in continuous lamination boardstock foams for commercial roof and residential wall insulation, as well as metal-faced panels, spray foams, and fire-rated doors.
Each of the above disclosed materials utilized in the foams of the present invention are described hereinafter.
(1) Isocyanate: Any organic polyisocyanates may be used in the practice of the invention. A preferred isocyanate is polyphenylene polymethylene polyisocyanate (PMDI). A most preferred isocyanate is those PMDI with diphenyl methane diisocyanate content of about 15 to about 42% by weight based on 100% by weight of the isocyanate.
The amount of isocyanate is typically about 30-75%, more preferably about 40-70% and most preferably about 45-65% by weight based on 100% of the total foam formulation.
(2a) HFC blowing agent: Any of the C1-C4 hydrofluorocarbons which are vaporizable under the foaming conditions can be used alone or as mixtures. Suitable HFCs include difluoromethane (HFC-32); trifluoromethane (HFC-23); 1,1-difluoroethane (HFC-152a); 1,1,1-trifluroethane (HFC-143a); 1,1,1,2-tetrafluoroethane (HFC-134a); pentafluoroethane (HFC-125); all isomers of pentafluoropropane (HFC-245 fa, ca, eb, ea etc.); all isomers of heptafluoropropane (HFC-236 ca, cb, ea, eb); isomers of pentaflurobutane (HFC-365); 1,1,1,4,4,4-hexafluorobutane (HFC-356mffm). Preferred HFCs include 1,1,1,3,3-pentafluoropropane (HFC-245fa); 1,1,1,3,3-pentaflurobutane (HFC-365mfc). Most preferred is HFC-245fa.
Other blowing agents, especially air, nitrogen, carbon dioxide, alkanes, alkenes, ethers may be used as the minor physical blowing agent. Representative alkanes include n-butane, n-pentane, isopentane, cyclopentane and mixtures thereof. Representative alkenes include 1-pentene. Representative ethers include dimethyl ether.
(2b) Water: Water reacts with isocyanate under foam forming conditions to liberate CO2. Water could be used with any of the physical blowing agents specified in 2(a).
The blowing agents are employed in an amount sufficient to give the resultant foam the desired density between 1.2 to 4.2 lb/cu.ft, preferably 1.4 to 4.0 lb/cu. ft., and most preferably 1.6 to 3.8 lb/cu. ft. Additionally, the amount of HFC used is such that the gaseous mixture in the closed cell of the rigid foam when initially prepared is between about 99-20%, preferably about 97-30%, most preferably about 95-40% molar percent HFC.
(3) Polyfunctional isocyanate-reactive compositions: These typically contain over about 40 weight % of aromatic polyester polyols of average functionality less than 3, the remaining being other types of isocyanate-reactive compound.
Suitable aromatic polyester polyols include those prepared by reaction a polycarboxylic acid and/or a derivative thereof or an anhydride with a polyhydric alcohol, wherein at least one of these reactants is aromatic. The polycarboxylic acids may be any of the known aliphatic, cycloaliphatic, aromatic, and/or heterocyclic polycarboxylic acids and may be substituted, (e.g., with halogen atoms) and/or unsaturated. Examples of suitable polycarboxylic acids and anhydrides include oxalic acid, malonic acid, glutaric acid, pimelic acid, succinic acid, adipic acid, suberic acid, azelaic acid, sebacic acid, phthalic acid, isophthalic acid, terephthalic acid, trimellitic acid, trimellitic acid anhydride, pyromellitic dianhydride, phthalic acid anhydride, tetrahydrophthalic acid anhydride, hexahydrophthalic acid anhydride, endomethylene tetrahydrophthalic acid anhydride, glutaric acid anhydride acid, maleic acid, maleic acid anhydride, fumaric acid, and dimeric and trimeric fatty acids, such as those of oleic acid which may be in admixture with monomeric fatty acids. Simple esters of polycarboxylic acids may also be used such as terephthalic acid dimethylester, terephthalic acid bisglycol and extracts thereof.
Examples of suitable aromatic polycarboxylic acids are: phthalic acid, isophthalic acid, terephthalic acid, and trimellitic acid. Suitable aromatic polycarboxylic acid derivatives are: dimethyl or diethyl esters of polycarboxylic acids such as phthalic acid, isophthalic acid, terephthalic acid, and trimellitic acid. Examples of suitable aromatic anhydrides are phthalic anhydride, tetrahydrophthalic anhydride, and pyromellitic anhydride.
While the polyester polyols can be prepared from substantially pure reactant materials as listed above, more complex ingredients may be advantageously used, such as the side-streams, waste or scrap residues from the manufacture of phthalic acid, phthalic anhydride, terephthalic acid, dimethyl terephthalate, polyethylene terephthalate, and the like.
The polyhydric alcohols suitable for the preparation of polyester polyols may be aliphatic, cycloaliphatic, aromatic, and/or heterocyclic. The polyhydric alcohols optionally may include substituents which are inert in the reaction, for example, chlorine and bromine substituents, and/or may be unsaturated. Suitable amino alcohols, such as monoethanolamine, diethanolamine or the like may also be used. Examples of suitable polyhydric alcohols include ethylene glycol, propylene glycol, polyoxyalkylene glycols (such as diethylene glycol, polyethylene glycol, dipropylene glycol and polypropylene glycol), glycerol and trimethylolpropane. Examples of suitable aromatic polyhydric alcohols are 1,4, benzene diol, hydroquinone di (2-hydroxyethyl) ether, bis (hydroxyethyl) terephthalate, and resorcinol.
The polyester polyol utilized in the present invention is aromatic and has an average functionality of less than 3. Thus, either the polycarboxylic acid (and/or a derivative thereof or an anhydride component) or the polyhydric alcohol or both are aromatic and the average functionality of reaction product is less than 3.0. There are a number of such polyols commercially available. STEPANPOL(copyright) PS-2352, PS-2402, PS-3152 are some such polyols manufactured by the Stepan Company. TERATE(copyright) 2541, 254, 403, 203 are some such polyols, manufactured by Hoechst-Celanese Corporation,. TEROL(copyright) 235, 235N, 250 are some such polyols manufactured by Oxid, Inc.
The polyfunctional isocyanate-reactive compositions may contain up to 60% of other suitable isocyanate-reactive compounds. Examples of such compositions include polyether polyols, aliphatic polyester polyols and mixtures thereof, having equivalent weights from about 40 to about 4000 of preferably about 50 to about 3000 and average hydroxyl functionalities of about 2 to about 8 and preferably about 2 to about 6. Further examples of suitable polyfunctional isocyanate-reactive compositions include active hydrogen-terminated polythioethers, polyamides, polyester amides, polycarbonates, polyacetals, polyolefins and polysiloxanes. Additional useful isocyanate-reactive materials include primary and secondary diamines (Unilink 4200), enamines, cyclic ureas, cyclic carbonate, and polycarboxylic acid. Some of these compounds react with isocyanate to evolve carbon dioxide and contribute to foam blowing.
(4) Organo-phosphorous compounds: Various phosphorous-containing organic compounds can be used. Suitable compounds include phosphates, phosphites, phosphonates, polyphosphates, polyphosphites, polyphosphonates, ammonium polyphosphate. Suitable phosphate compounds are of the following formula: 
where R1 to R3 signifies alkyl, halogen substituted alkyl, aryl, halogen substituted aryl and cycloalkyl groups. Preferred phosphates are those where R1 to R3 signifies C1-C12 alkyl, C1-C12 halogen substituted alkyl, phenyl, cresyl, halogen substituted phenyl and C5-C10 cycloalkyl groups. More preferred phosphates are those where R1 to R3 signifies C1-C8 alkyl, C1-C8 halogen substituted alkyl, and phenyl groups. Most preferred phosphate compounds are those where R1 to R3 signifies C1-C4 alkyl, C1-C4 halogen substituted alkyl, and phenyl groups. Some specific compounds under most preferred phosphates are tributyl phosphate, tris(2-chloropropyl)-phosphate (Antiblaze 80 from Albright and Wilson), t-butylphenyl diphenylphosphate (Phosflex 71B from Akzo Nobel), triethyl phosphate (TEP from Eastman), tributyl phosphate (Phosflex 4 from Akzo Nobel), chloropropyl bis(bromopropyl) phosphate (Firemaster FM836 from Great Lakes).
Suitable phosphite compounds are of the following formula: 
where R1 to R3 signifies H, alkyl, halogen substituted alkyl, aryl, halogen substituted aryl and cycloalkyl groups. Preferred phosphites are those where R1 to R3 signifies C1-C12 alkyl, C1-C12 halogen substituted alkyl, phenyl, cresyl, halogen substituted phenyl and C5-C10 cycloalkyl groups. More preferred phosphites are those where R1 to R3 signifies, C1-C8 alkyl, C1-C8 halogen substituted alkyl, and phenyl groups. Most preferred phosphite compounds are those where R1 to R3 signifies C1-C4 alkyl, C1-C4 halogen substituted alkyl, and phenyl groups. Some especially suitable phosphates are triethyl phosphite (Albrite TEP from Albright and Wilson), tris(2-chloroethyl)-phosphite, and triphenyl phosphite (Albrite TPP).
Suitable phosphonate compounds are of the following formula: 
where R1 to R3 signifies alkyl, halogen substituted alkyl, aryl, halogen substituted aryl and cycloalkyl groups. Preferred phosphonates are those where R1 to R3 signifies C1-C12 alkyl, C1-C12 halogen substituted alkyl, phenyl, cresyl, halogen substituted phenyl and C5-C10 cycloalkyl groups. More preferred phosphonates are those where R1 to R3 signifies C1-C8 alkyl, C1-C8 halogen substituted alkyl, and phenyl groups. Most preferred phosphonate compounds are those where R1 to R3 signifies C1-C4 alkyl, C1-C4 halogen substituted alkyl, and phenyl groups. Some especially suitable phosphonates are diethyl ethyl phosphonate (Amgard V490 from Albright and Wilson), dimethyl methyl phosphanate (Amgard DMMP), bis(2-chloroethyl), and 2-chloroethyl phosphonate.
Illustrative examples of polyphosphate compound are Amgaurd V-6, a chlorinated diphosphate ester, from AandW. Illustrative examples of ammonium polyphosphate [(NH4PO3)n; n=about 1000) is Hostaflam AP 422 from Hoechst AG.
The organo-phosphorous compounds used in the invention may have one or more isocyanate-reactive hydrogen comprising of hydroxyl group, amino group, thio group, or mixture thereof. Suitable compounds include monomeric or oligomeric phosphates, phosphites, and phosphonates polyols. Suitable isocyanate-reactive phosphate compounds are those prepared by (1) the reaction of polyalkylene oxides with (a) phosphoric acids (b) partial esters of phosphoric acids; (2) the reaction of aliphatic alcohols with (a) phosphoric acids (b) partial esters of phosphoric acids; and (3) by transesterification of products of (1) and (2). The preferred compounds include tributoxyethyl phosphate (Phosflex T-BEP from Akzo); oligomeric organophosphate diol (Hostaflam TP OP 550 from Hoechst AG); ethoxylated phosphate esters (Unithox X-5126 from Petrolite); and mono- and diesters of phosphoric acid and alcohols (Unithox X-1070 from Petrolite).
Suitable isocyanate-reactive phosphite compounds are those prepared by (1) the reaction of polyalkylene oxides with (a) phosphorous acids (b) partial esters of phosphorous acids; (2) the reaction of aliphatic alcohols with (a) phosphorous acids (b) partial esters of phosphorous acids; and (3) by transesterification of products of (1) and (2).
Suitable isocyanate-reactive phosphonate compounds are those prepared (1) by the reaction of polyalkylene oxides with phosphonic acids, (2) by the reaction of phosphite polyols with alkyl halides; (3) by the condensation of dialkyl phosphonates, diethanolamine and formaldehyde; (4) by transesterification of products of (1) (2) and (3); and (5) by reaction of dialkyl alkyl phosphonate with phosphorous pentaoxide and alkylene oxide. The preferred compounds include diethyl N,N-bis(2-hydroxyethyl) aminoethyl phosphonate (Fyrol 6 from Akzo); hydroxyl containing oligomeric phosphonate (Fyrol 51 from Akzo).
The amount of said organo-phosphorous compound used is such that the amount of phosphorous is between about 0.01 to about 2.5% by weight, based on the total weight of the foam forming reaction mixture. Preferred amount of phosphorous is between about 0.025 to about 1.5% and most preferred is about 0.05 to about 1.0% by weight, based on the total weight of the foam forming reaction mixture.
(5) Additives: The resin side can also contain various auxiliary agents and additives as needed for a particular purpose. Suitable auxiliaries and additives include crosslinking agents, such as triethanolamine and glycerol; foam stabilizing agents or surfactants, such as siloxane-oxyalkylene copolymers; oxyethylene-oxyalkylene copolymer; catalysts, such as tertiary amines, (e.g., dimethylcyclohexylamine, pentamethyldiethylenetriamine, 2,4,6-tris(dimethylaminomethyl) phenol, triethylenediamine); organometallic compounds (e.g., potassium octoate, potassium acetate, dibutyl tin dilaurate), quaternary ammonium salts (e.g., 2-hydroxypropyl trimethylammonium formate) and n-substituted triazines (N, Nxe2x80x2, Nxe2x80x3-dimethylaminopropylhexahydrotriazine); viscosity reducers such as propylene carbonate, 1-methyl-2-pyrrolidinone; infra-red opacifiers such as carbon black, titanium dioxide, metal flakes; cell-size reducing compounds such as inert, insoluble fluorinated compounds, perfluorinated compounds; reinforcing agent such as glass fibers, ground up foam waste; mold release agents, such as zinc stearate; antioxidents, such as butylated hydroxy toluene; and pigments such as azo-/diazo dyestuff, phthalocyanines.
Amount of such additives are generally between about 0.1-20%, preferably between about 0.3-15% and most preferably between about 0.5-10%, by weight based on 100% of the total foam formulation.
In carrying out the process for making rigid foams according to this invention, the known one-shot, prepolymer or semi-prepolymer techniques may be used together with conventional mixing methods including impingement mixing. The rigid foam may be produced in the form of slabstock, mouldings, cavity filling, sprayed foam, frothed foam or laminates with other material such as paper, metal, plastics, or wood-board.
The various aspects of this invention are illustrated, but not limited by, the following examples. Unless otherwise noted, all temperatures are expressed in degrees Celsius and all formulation components are expressed in parts by weight.